P0879Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. They are more widespread than A and B: GM's 6L80/6L90 and 6T40/6T70 six-speeds put switch C on the 2-6 brake and D on the 1-2-3-4 clutch, Allison uses them for its third shift valve and its reverse switch, Ram's RFE gearboxes for the clutch pressure switches in the solenoid block. Ford reports pressure faults under its solenoid codes. P0879 reports short dropouts of the D signal. Like P0874 it is documented only for the Corvette C8 dual clutch in GM bulletin 21-NA-033, with MIL: clean the valves, relearn, then trace the circuit if the code returns. No thresholds are published.
- What you may notice
- Warning lamp coming and going
- Occasional harsh shift or limp mode
- Likely causes
- LikelyLoose contact or corrosion at connector or harness
- PossibleDirt or sticking valve (dual clutch)
- PossibleSensor or switch with dropouts
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.